Viewed through the window of an airplane, the Colorado River just seems so unlikely. On a cross-country flight this New Year’s Day, I watched as the snow-covered Rockies gave way to pancaked expanses of red rock. At its headwaters in the mountain foothills, the Colorado makes sense. But as I watched it flow through the deep scars that its waters had carved into a desiccated landscape, the river felt strange.

As a native of drought-ridden Southern California, the Colorado River has always loome...